IQ Score Ranges Explained.
IQ ranges look like discrete categories - average, above average, gifted - but underneath them is a single smooth curve. Scores are scaled so that 100 is the population average and every 15 points is one standard deviation, which fixes how common each range is. The "classifications" are just convenient names for slices of that curve.
IQ score ranges
IQ score ranges are conventional labels mapped onto the bell curve, where the mean is 100 and the standard deviation is 15. The common bands are: below 70 (about the bottom 2 percent), 70-84 (below average), 85-114 (average, where roughly 68 percent of people fall), 115-129 (above average), and 130 and up (about the top 2 percent, often labeled gifted or very superior). The labels are useful summaries, not hard biological lines, and a score near a boundary should never be read as categorically different from one just across it.
This page lays out the standard bands, the percentile behind each one, and the bell-curve logic that ties them together. It also makes a point that score reports often gloss over: the boundaries are conventions. Someone at 129 and someone at 131 are, for all practical purposes, the same; the band label changes, the person does not.
The bell curve behind the bands
IQ scores follow an approximately normal distribution, the symmetric bell curve. The peak sits at 100, and scores thin out evenly on both sides. Because the standard deviation is 15, fixed proportions of people fall within each step: about 68 percent score within one standard deviation of the mean (85 to 115), about 95 percent within two (70 to 130), and about 99.7 percent within three (55 to 145).
This is why the ranges are not arbitrary even though the labels are conventional. Once you fix the mean at 100 and the standard deviation at 15, the rarity of every score is determined by the math. A range is simply a way of naming a region of the curve and the slice of the population it covers.
The standard IQ ranges and their percentiles
The bands below are the most widely used convention. The percentile tells you the share of people you scored at or above; the population share tells you how common the band is. Different test publishers use slightly different cutoffs and label wording, so treat the numbers as close approximations rather than exact lines.
- 130 and above - about the 98th percentile and up (top ~2%); often labeled "gifted" or "very superior"
- 115 to 129 - roughly the 84th to 98th percentile; "above average" or "high average to superior"
- 85 to 114 - roughly the 16th to 84th percentile; "average," where about 68% of people fall
- 70 to 84 - roughly the 2nd to 16th percentile; "below average" or "borderline"
- Below 70 - about the bottom 2%; in clinical settings, one of several criteria considered, never a label applied from a score alone
Why most people are "average" - and that is the point
The single most common fact about IQ ranges is also the most reassuring: roughly two-thirds of everyone scores in the average band of 85 to 115. The bell curve is densest in the middle by design, so "average" is not a consolation category - it is where most of the human population lives, including a great many highly capable, accomplished people.
It also means the extreme labels describe rare positions, not different kinds of people. Only about 1 in 50 reaches 130, and only about 1 in 50 falls below 70. The further a score sits from 100 in either direction, the rarer it is and the larger the measurement uncertainty around it becomes.
Why the labels are conventions, not hard lines
Band names are administrative conventions placed on a continuous scale. There is no biological switch that flips at 130 or 70; the curve is smooth all the way through. A two-point gap that happens to straddle a cutoff carries no real meaning, yet it changes which label a report prints - a quirk of categorizing a continuum, not a fact about ability.
Two further cautions follow. First, every score carries measurement error, so a single number is best read as a band of plausible values, which is why honest tests (including ours) report a range with a percentile rather than a false-precision point. Second, a low score is never a diagnosis: clinical classifications rest on standardized testing plus assessment of everyday functioning by a qualified professional, never on an online number alone.
Also relevant: See a sample IQ report
Frequently asked questions
What is a normal IQ range?
The normal or average range is usually given as 85 to 115, which is one standard deviation either side of the mean of 100. About 68 percent of people score in this band, so it covers the large majority of the population.
What percentage of people fall in each IQ range?
Roughly 68 percent score 85 to 115, about 14 percent fall in 70 to 84 and another 14 percent in 115 to 129, and about 2 percent sit below 70 with about 2 percent above 130. These proportions come directly from the bell curve with a mean of 100 and a standard deviation of 15.
What IQ range is considered gifted?
130 and above is the conventional threshold for the gifted or very superior range, corresponding to roughly the top 2 percent of scores. The exact cutoff and label vary by test publisher and program, and researchers note that exceptional achievement depends on far more than a test score.
Are IQ classification labels official?
No. They are widely used conventions, not a single official standard, and different publishers use slightly different cutoffs and wording. They are summaries of regions on a continuous curve, so a score near a boundary should not be treated as categorically different from one just across it.
References
- Deary, I. J. (2012). Intelligence. Annual Review of Psychology, 63, 453-482.
- Neisser, U., Boodoo, G., Bouchard, T. J., et al. (1996). Intelligence: Knowns and unknowns. American Psychologist, 51(2), 77-101.
- Gottfredson, L. S. (1997). Why g matters: The complexity of everyday life. Intelligence, 24(1), 79-132.
Built and led by a PhD psychometrician who designed international assessment frameworks for the OECD. About the team · How our tests are built and validated